JPH03260129A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To obtain the subject tire having excellent high-speed durability by embedding a specific composite fiber suitable as a rubber-reinforcing material into a cap layer and/or a carcass ply layer. CONSTITUTION:A cord composed of filaments having sheath-core structure is embedded in a carcass ply layer and/or a cap layer. The core part of the filament is made of a polyester and the sheath part is a blended mixture of 70-99wt.% of a polyamide and 30-1wt.% of a polyester. The outer circumference of the core part and the inner circumference of the sheath part have hooking protrusions and recesses corresponding to each other and the core part is fit and bonded to the sheath part.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a pneumatic radial tire reinforced with high-strength tire reinforcing fibers, which has excellent adhesion to rubber, and has excellent heat resistance and fatigue resistance in rubber. This invention relates to a pneumatic radial tire that is reinforced with high-strength tire-reinforcing fibers that have excellent properties such as elasticity, and has improved high-speed durability.

(Prior Art) Polyester fibers, typified by polyethylene terephthalate fibers, have the characteristics of high strength and high elastic modulus, and are therefore widely used in various industrial material applications. It is said to be particularly useful as tire cord.

However, polyester fibers generally have poor heat resistance in rubber, and at high temperatures, the ester bonds of polyester fibers are broken by the action of moisture and amine compounds in the rubber, causing a decrease in strength and adhesion to rubber. Sexually inferior,
In particular, there is a problem in that the adhesive strength with rubber decreases when exposed repeatedly for a long time in a high temperature atmosphere.

In response to this, many attempts have been proposed to improve the adhesion, which is a drawback of polyester fibers for rubber reinforcement, and one known method is to coat the surface of polyester fibers with polyamide. For example, Japanese Patent Application Laid-Open No. 49-85315 describes a method for producing composite fibers having a polyester core and a nylon 6 sheath. It is described that it is used as a tire reinforcing material.

Japanese Patent Publication No. 62-42061 also discloses that the fiber is made of a core-sheath type composite structure in which the core is polyester and the sheath is polyamide, and the polyamide-sheath component is 70 to 30% by weight, and the surface is coated with an epoxy adhesive. It is described that the rubber reinforcing fibers attached by the method are used as a tire reinforcing material.

In JP-A-1-97211, the core is made of polyester,
66/6T copolyamide is used for the sheath, and the copolymerization ratio of hexamethylene diammonium terephthalate in the 66/6T copolyamide is 5% by weight or more, preferably 10% by weight.
~40% by weight of core polyester and sheath 66
The use of rubber reinforcing fibers with improved boundary adhesion with /6T copolyamide is described as a tire reinforcing material.

In JP-A-1-97212, the adhesion at the interface is improved by making the core polyester and the sheath xamethylene diammonium terephthalate polyamide into a highly oriented, highly crystalline fiber structure, and by using this fiber, tire performance is improved. It describes what can be done.

Special Publication No. Sho 49-85315, Special Publication No. Sho 62-4206
Publication No. 1 states that the use of polyamide in the sheath improves the adhesion with rubber, which is a disadvantage of polyester fibers, and furthermore, it has the effect of suppressing amine decomposition. And, Japanese Patent Application Publication No. 1-97211,
Although JP-A-1-97212 improves the boundary adhesion between the core polyester and the sheath polyamide, a sufficient improvement effect is not recognized.

Therefore, in pneumatic tires that use conventional composite fibers as reinforcing materials, the core-sheath polymer interface is destroyed and the sheath is then separated and fractured due to repeated elongation and compression fatigue during tire running. The original performance of composite fibers is not being demonstrated.

(Problems to be Solved by the Invention) The present invention has excellent adhesion to rubber, as well as Young's modulus and
The present invention relates to providing a pneumatic radial tire reinforced with high-strength composite fibers that have excellent dimensional stability, heat resistance and fatigue resistance in rubber, and are suitable as rubber reinforcing materials. It has improved bonding strength, has sufficient durability against interfacial peeling between core-sheath polymers, and has high-speed durability reinforced with rubber-reinforcing composite fibers that fully exhibit the characteristics of composite fibers over a long period of time. To provide an excellent pneumatic radial tire.

(Means for Solving the Problems) As a result of extensive research to solve the above problems, the present inventors have found that at least one layer of the carcass ply layer or the cord of the cap layer is made of filaments having a core-sheath structure. It was confirmed that the above problem could be solved by using a cord, using polyester for the core, a blend of polyamide and polyester for the sheath, and providing unevenness to the core-sheath interface, leading to the completion of this invention. .

That is, the present invention provides a pneumatic radial tire comprising a carcass ply layer in which cords are arranged in a substantially radial manner and a plurality of belt layers surrounding the outer periphery of the crown portion of the carcass ply layer. A cord in which at least one layer of the cap layer forming the outer layer is made by twisting filaments having a core-sheath structure consisting of a core and a sheath wrapped around the core with a polymer different from the polymer forming the core. is embedded in rubber, and the outer circumferential surface of the core and the inner circumferential surface of the sheath have corresponding and opposite hooking irregularities, so that the core and the sheath are fitted and bonded to each other. The polymer forming the sheath is made of polyamide 7.
It is a mixture of 0 to 99% by weight and 30 to 1% by weight of polyester, and the polymer constituting the core is polyester,
It is a pneumatic radial tire in which the core accounts for 30 to 90% by weight of the total weight of the core and sheath.

(Function) The pneumatic radial tire of this invention is shown in Fig. 1.
As shown in the example, a carcass ply layer 2 having a substantially radial arrangement of cords is folded back around the bead 11, and a plurality of belt layers, in this case two belts Ji! 3.4, of which the outermost belt layer is called a cap layer layer, and at least one layer of the carcass ply layer and the cap layer layer contains a cord made of twisted core-sheath filaments as a cord component. That is.

That is, the filament has a shape as shown in FIGS. 2 and 3, with an uneven interface between the core and sheath so that the core and sheath fit and adhere to each other. , thereby improving the adhesive strength of the interface.

For example, the filament of FIG. 2a consists of a core 11 (the area indicated by the horizontal lines) and a sheath 12 surrounding it and made of a different polymeric material than the core, and as seen in the cross-sectional view, the filament has a core 11 (the area indicated by the horizontal line) and a sheath 12 of a different polymeric material than the core. The core part 11 and the sheath part 12 are fitted and bonded to each other because the inner circumferential surface of the sheath part has recesses and recesses that are opposite to each other and engage with each other.

In this case, the tips of the protrusions 13 on the outer circumferential surface of the core and the inner circumferential surface of the sheath protrude to both sides and are fitted into and adhered to correspondingly shaped recesses of the other, and the protrusions 13 on the inner circumferential surface of the sheath have the same shape. The height of the protrusion (a) measured toward the center of the filament is 5 to 30 times the maximum width of the filament (D), which is the length connecting the two farthest points on the filament contour line.
%, the hooking length (b) indicated by the lateral overhang width of the protrusion is 5 to 30% of the maximum filament width CD), and the width of the base (c) is the maximum filament width (D). It is preferable that it is 5 to 30% of .

Furthermore, the height (a) of the protrusion, the length of the hook (b), and the width of the base (c) are each 10% of the filament maximum width (D).
More preferably, it is 20%.

It is preferable that the number of protrusions is two or more.

If a, b, and c are less than 5% of the maximum cross-sectional width (D) of the filament, there will be little catching, and the peeling durability of the polymer at the core-sheath composite interface will be poor, and if it exceeds 30%, the protrusion will be Difficult to secure numbers. More preferably, the range of a, b, and c relative to D is 10 to 20%.

For example, when examining the durability of a tire cord made of filaments with a concentric core-sheath cross section where a, b, c = 0%, it was found that during running the core-sheath interface polymer It was confirmed that peeling failure was likely to occur between the two.

Such conditions can be applied to all the uneven core-sheath filaments as shown in FIGS. 2b to 2c and 38 to 3c.

The cross-sectional shape of the core-sheath type filament is not limited to the circular cross-section shown in FIG. 2a, but may also be triangular (FIG. 2b) or elliptical (FIG. 2c).

Furthermore, the shape parameters a, b, and c of the protrusion 13 can suitably vary within a range of 5 to 30% with respect to the maximum width;
a = b = c = 5% as shown in Figure 3a, a = b = 20% as shown in Figure 3b, C = 25%, a = b = c = 10% as shown in Figure 3c. It can be used in various types such as.

Next, in the filament used in the pneumatic radial tire of the present invention, the polymer constituting the sheath portion is polyamide 70.
It is a mixture of ~99% by weight and 30-1% by weight of polyester, and the polymer constituting the core is polyester, which allows for even better adhesion at the interface between the core and sheath. The content of polyester in the sheath is usually preferably 30 to 5% by weight. 3
If it exceeds 0% by weight, the properties of the polyamide fiber expected for the sheath component, especially heat-resistant adhesiveness and heat resistance in rubber, will deteriorate. On the other hand, if it is less than 1% by weight, the effect of improving the adhesion of the core-sheath composite interface is not clear, and the effects of the present invention cannot be obtained. The polyester polymer used as part of the sheath component is preferably the same as the polymer used as the core component described below, but does not necessarily have to be the same.

The polyester of the polymer constituting the core is preferably a polyester consisting essentially of ethylene terephthalate units, and the copolymer content is such that it does not substantially reduce the physical and chemical properties of the polyethylene terephthalate polymer, for example, less than 10% of the copolymer component. may also be included. Copolymerization components include dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid, and propylene glycol.
It may also contain a diol component such as butylene glycol, ethylene oxide, etc. And strength of core-sheath composite fiber 7
．． In order to obtain 5 g/d or more, the core polyethylene terephthalate polymer has a high intrinsic viscosity ([η]) of 0.8 or more, preferably 0.9 or more.

In addition, in order to obtain excellent heat resistance in the rubber of the core-sheath composite fiber, the concentration of carboxyl end groups in the polyester core is 2.
It is preferably 0 eq/10'g or less.

The polyamide used as the main component of the sheath includes ordinary polyamides such as polycabramide, polyhexamethylene adiva ξ-do, polytetramethylene adipamide, polyhexamethylene dodecamide, polyhexamethylene dodecamide, and some components thereof. It is selected from polymers and blends of the above polyamides, with polyhexamethylene adipamide-based polymers being preferred. The polyamide polymer also needs to have a high degree of polymerization in order to obtain the composite fiber used in the present invention, and has a sulfuric acid relative viscosity (ηr) of 2.7 or more, preferably 3.0 or more.

The ratio of the core portion of the core-sheath composite fiber used in the pneumatic tire of the present invention is 30 to 90% by weight. If the core proportion is less than 30% by weight, it is difficult to achieve the same level of modulus and dimensional stability as polyester as a composite fiber. On the other hand, if the polyester core exceeds 90% by weight, improvements in adhesion between the composite fiber and rubber, heat resistance in rubber, etc. cannot be sufficiently achieved.

The composite fiber used in the present invention is characterized in that both the sheath made of a mixed polymer of polyester and polyamide and the polyester core are highly oriented and crystallized. In other words, the birefringence (Δn) of the polyester core is 1
60X10-' to 19θX10-'. 160
If less than X 10-', the strength (T/D) of the composite fiber is 7
．． 5g/d or more, initial tensile resistance (Mi) 60g
It cannot be greater than /d. On the other hand, 190X10-
If it exceeds ', dimensional stability and fatigue resistance will not be improved. According to the new method for producing composite fibers used in the present invention, which will be described later, the birefringence usually does not exceed 190 Xl0-'.

On the other hand, the birefringence (Δn) of the polyamide component, which is the main component constituting the sheath, is 50XIO-z or more, preferably 55XI
It is highly oriented, with a birefringence of 50 x 10-
If it is less than 10%, a composite fiber with high strength and high initial tensile resistance cannot be obtained.

The birefringence of a core-sheath composite fiber can be measured as follows. That is, the sheath was measured as it was with a transmission interference microscope, and the core was sampled by dissolving the polyamide component, which is the main component of the sheath, with formic acid, sulfuric acid, fluorinated alcohol, etc., and only the core polyester component fiber was sampled. Measure using transmission interference microscopy or the usual Berek compensator method.

The density of the polyester core component is measured by dissolving and removing the polyamide component with formic acid, sulfuric acid, fluorinated alcohol, or the like. The density of the polyamide, which is the main component of the sheath, can be calculated from the density of the composite fiber, the density of the polyester component, and the composite ratio.

The composite fiber used in the present invention characterized by the above fiber structure has a high strength of 7.5 g/d or more, an initial tensile resistance of 60 g/d or more, and a dry heat shrinkage rate ( Δsrs.) exhibits fiber properties of 7% or less.

More preferable composite fiber properties include strength of 8 g/d or more, initial tensile resistance of 70 g/d or more, and dry heat shrinkage rate (Δ51.

) is less than 5%, which is achieved by a proper combination of the fiber structure properties mentioned above.

The composite fiber used in the pneumatic radial tire of the present invention having the above characteristics is produced by the novel method described below.

In order to obtain the polyester fiber physical properties of the core, a polymer consisting essentially of polyethylene terephthalate and having an intrinsic viscosity ([η1) of 0.80 or more, usually 0.85 or more is used. Furthermore, in order to obtain fibers with excellent heat resistance, it is preferable to spin a polymer having a low concentration of carboxyl terminal groups. For example, techniques such as employing a low-temperature polymerization method or adding a sealing material during the polymerization process or spinning process are applied. Examples of blocking agents include oxazolines, epoxies, carbodiimides, ethylene carbonate, oxalate esters,
These include malonic acid esters.

(Examples) Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Production of core-sheath type filaments When producing core-sheath type filaments, two steps are required for melt spinning.
Using an extruder-type spinning machine, one extruder melts a mixed polymer of polyester and polyamide for the sheath, the other extruder melts the polyester for the core, and the remelted polymers are each melted. 6.6 into a composite spinning pack and using equipment similar to known spinning equipment as described in Japanese Patent Publication No. 18369/1983.
- A mixed polymer of nylon (66Ny) and polyethylene terephthalate (hereinafter referred to as PET) is used for the sheath and P
A core-sheath type filament with a total denier of 1500 deniers in which ET is the core was produced. In this case, the diameter of the hole in the spinneret and the amount of polymer discharged are adjusted to control the weight ratio of PET +6.6-nylon/6,6-nylon, and the shape of the spinneret is adjusted to the desired core-sheath interface shape of the filament cross section. A desired core-sheath shape was obtained by shaping the core to match the shape.

Confirmation of core-sheath structure and a, b, c of Figures 2-3.

The value of D is determined by scanning the filament cross section with a scanning electron microscope (SE
It was calculated by measurement from the photograph taken in M).

The percentage of the core to the total of the core and sheath is calculated from the area ratio determined from a cross-sectional micrograph of the filament sample and the density.

The percentage of polyamide in the core is calculated from the percentage of the core determined above by treating the filament sample with formic acid, dissolving and removing the polyamide component, and measuring the polyester component (core sheath).

The intrinsic viscosity of PET is orthochlorophenol (25°
C).

PET terminal carboxyl group (cOOH) is determined by adding 1 g of PH7 sample to 20 ad! of orthocresol! After complete dissolution, 40 m of chloroform was added after cooling, and the amount was determined by potentiometric titration with a methanol solution of caustic soda.

1-3, 1-3 Manufacture of tires The cord made from the filament manufactured as described above is used as the cap layer layer (outermost belt layer, sometimes referred to as the 2-18 layer) of a 195/70R14 size radial tire. used as the code. As shown in FIG. 1, this tire has a cord A layer 3 as a belt layer on a carcass ply M2, and is further reinforced with a two-18 layer (cap layer) 4 thereon. Two 18
The number of embedded cords in the layer is 50 15c111, and the cord in the code A layer is steel cord (I x 5
Xo, 23+l1m) was used. In addition, the carcass ply layer 2 is made of PET cord (1500d/3.30
) has a single layer structure.

The cord used for the cap layer 4 was a cord made from six types of trial filaments shown in Table 1 below.

The tire was tested using the test method shown below.

(a) Adhesive strength of cord A cord was embedded in rubber, and after vulcanization, the peel resistance when the cord was taken out was determined according to JIS-6301.

(mouth) Tire drum test: High speed test (Table 1) According to the test method of the American standard FMVSS k 109, the step speed method was used, and the speed was increased every 30 minutes at 8 km / hour until failure occurred. The speed (km/hour) and time (minutes) were measured.

The test results are shown in Table 1.

As is clear from Table 1, adhesive strength and high-speed durability increased by increasing the values of a, b, and c. When the protrusions a, b, and c are in the range of 5 to 30%, improvements in adhesive strength and high-speed durability can be seen compared to Comparative Example 3.
The above improvement is significant at 20%.

Next, the relationship between the weight percent of polyester mixed with polyamide in the sheath and high-speed durability is as shown in Examples 1 to 3. As the weight percent of polyamide increases, the interfacial adhesion between the core and sheath increases. As a result, high speed is significantly improved. However, in Comparative Example 2, the weight percent of polyamide was 30
% by weight, resulting in poor adhesive strength and high speed performance. The weight percent of polyester mixed with polyamide is 1 to 30% of the total weight.
It is necessary that the amount is % by weight.

4-6, 4-6 Manufacture of Tire The filaments used in Examples 1-3 and Comparative Examples 1-3 were respectively used to make cords, and these cords were applied to the carcass ply layer. That is, the code is 100
Five sheets were used as carcass material for 0R2014PR size truck and bus tires, with the number of embedded cords being 50 cords/5 cm. A 3+6 twisted steel cord was used as the belt cord.

The following tests were conducted using this tire.

(C) Long drum carcass durability test (Table 2) Test tires were applied to a drum with a diameter of 3.5 m under the conditions of normal internal pressure and a load of 20% more than the normal internal pressure to 5,000,000 +++ (
The carcass cord was taken from the tire, the strength of the cord was measured at the shoulder part and the bead part, and the lower value was divided by the cord strength value when not running. Shown as a comparison of values (residual strength retention rate).

(d) Noise measurement (Table 2): Bench noise (dB) JASO (
A single tire bench test was conducted in accordance with C606-81 (Japan Society of Automotive Engineers of Japan). The outline of the test according to JSAOC606-81 is shown below.

Claims (1)

[Claims] 1. A pneumatic radial tire comprising a carcass ply layer in which cords are arranged in a substantially radial manner and a plurality of belt layers surrounding the outer periphery of the crown portion of the carcass ply layer, wherein the carcass ply layer and the belt layer At least one layer of the cap layer forming the outermost layer is made by twisting filaments having a core-sheath structure consisting of a core and a sheath wrapped around the core with a polymer different from the polymer constituting the core. The cord is embedded in rubber, and the outer circumferential surface of the core and the inner circumferential surface of the sheath have corresponding and opposite hooking unevenness so that the core and the sheath fit and adhere to each other. The polymer forming the sheath is a mixture of 70 to 99% by weight of polyamide and 30 to 1% by weight of polyester, and the polymer forming the core is polyester. A pneumatic radial tire characterized in that the pneumatic radial tire accounts for 30 to 90% by weight of the total weight of the core and sheath. 2. In the cross section of the filament, the tips of the protrusions on the outer circumferential surface of the core and the inner circumferential surface of the sheath protrude to both sides and fit tightly into the correspondingly shaped recesses of the other, and the inner circumferential surface of the sheath protrudes. The height (a) of the protruding part measured toward the center of the filament as the shape of the part is 5 to 30% of the filament maximum width (D) indicated by the length connecting the two furthest points on the filament contour line, The hooking length (b), which is indicated by the lateral width of the protrusion, is the maximum width of the filament (
2. The pneumatic radial tire according to claim 1, wherein the base width (c) is 5 to 30% of the filament maximum width (D). 3. The height of the protrusion (a), the length of the hook (b), and the width of the base (c) are each 10 to 10% of the maximum filament width (D).
The pneumatic radial tire according to claim 2, wherein the content is 20%. 4. The spaced radial tire according to any one of claims 1 to 3, wherein the number of protrusions is two or more.